PM66 One Belt Vibrates

[Jeffrey Kibler]

So my 8 year old powermatic 66 starting acting a little funny last month. A blade that used to make a mirror finish (absolutely zero blade marks) started leaving blade marks so I started with the obvious and got the blade sharpened. Got it back and it did the same thing, so I sent it to a better sharpening place with CNC machines and computer balancers and it still did the same thing when I got it back. That I went full blow crazy and basically overhauled the saw. I took it completely apart, replaced the arbor bearings, cleaned everything spotless, and put link belts on it.... still does the same thing.

I do notice a harmonic vibration with the saw running and I'm almost positive that is what is causing the blade to shake just a tiny bit. All of my blades do it so I know the blade isn't the problem. I have also noticed that the belt closest to the arbor visibly vibrates while the saw is running and the outter one is rock solid. I'm almost positive the pullys are lines up properly so this makes no sense to me.

I'm open to any suggestions. The saw used to cut flawlessly so this is really frustrating me. Now I just can't let it go. I'm really suprised the v-belts (power twist by fenner drives) are acting like they are.

PS... i'm new to sawmill creek and I love it. What a great community of people.

[John McClanahan]

I run with only 1 belt for that reason. I don't do heavy duty sawing, so the single belt hasn't been a problem.

John

[Chris Rosenberger]

Have you run the motor without the belts to the arbor to see if it has the same vibration?

[Bill Geibe]

When you run multiple belts like that, if they aren't absolutely, identically the same length one will get the shakes. I have a Unisaw with three belts. When I rebuilt the saw I put three premium Gates belts on it. Two flopped around noticeably and the saw vibrated, especially on coast-down. With Unisaws, the trick is to get three matched belts from Delta that are cut from the same batch with sequential numbers. That cured the problem.

All that being said, I'd be surprised if one belt being slightly loose is causing a cutting problem. My initial thought was loose arbor bearings but you took care of that.

Bill

[Jeffrey Kibler]

I'm actually worried that I should have just bought the pre-fabricated arbor assembly from powermatic instead of just replacing the bearings myself. Either way I'm going to go take one of the belts off and see what happens. I think 99% of the people out there would be more than happy with the quality of the cut, however I know what the saw is capable of and I'm having a hard time living with this problem. I used to be able to rip or crosscut 3/4" boards with this blade and then finish them with no sanding at all. I'll do some troubleshooting today and maybe post a quick video. Just in case anyone doesn't believe me here are some pics of the "overhaul" i did on the saw. I literally ripped it apart.
ts1.jpgts2.jpg

[John Lanciani]

Ditch the link belts and get a matched pair of the correct 3VX belts. Link belts are a problem solver for sure but they are a solution for problems that a PM66 does not have.

[Jeffrey Kibler]

Interesting. The reality is there is probably nothing wrong with the original belts. Maybe I'll toss one or two on there and try it when I'm playing around later.

[Randy Henry]

Went through the same thing as you did, except the reason I had to tear my 66 down was, the blade raise shaft locked up. Ended up doing a complete overhaul also. I noticed when I was taking mine apart, the pulley on the arbor shaft was not in line with the motor pulley, not even close, about 1/4" off. When I put it all back together, I moved the pulley in on the arbor shaft to where it was perfectly in-line with the motor pulley. The saw runs better than it ever has. It now makes the "mirror cuts" like you said. I used the same belts that were on it though.

[David Kumm]

Link belts are a poor choice for multiples as they never are exactly the same even if you count the links. Optibelts are manufactured to match without having to look for the same lot. Multiple belts have been largely replaced with single VX belts in newer machines. Dave

[Jeffrey Kibler]

So i'm pretty torqued right now. I took the belts off and started the motor and the exact vibration i was talking about was there. I knew immediately what that meant... so i started digging. Took off the big 5HP Baldor motor slowly spun the shaft and i could hear the pully side bearing grinding away. Took the motor apart, took the rotor out and spun the bearing and it was completely shot. I don't know if this was enough vibration to cause the blade marks i'm seeing but I guess we will find out when i get some new bearings installed.

The reason I'm kind of upset is that this motor was extremely expensive and it is designed to never get a drop of saw dust in it. Mine had plenty of very fine saw dust in it. I asked powermatic about a year after i got the saw if i should be greasing the motor periodically and they told me absolutely not. Fast forward 6 years I call them again when i start having these cut quality issues and ask them the same question.... they again say no. Now that i have the motor apart i'm positive they are wrong. The grease plugs on these motors are not for greasing the bearings... they are actualy designed to create a seal between the motor casing and the bearing making it so the motor is essentially sealed. When i pulled my motor apart there was only about 30 degrees of the 360degree cavity that had the grease seal still there. I'll be calling Baldor on Monday to see what they say, and if they say i should have been greasing the motor I think powermatic is going to be buying me some bearings.

I'm wondering if anyone else has had bearing problems with the baldor motors. I think i'm going to poke around and see what i find. Attached is a low quality video. If you listen close you can hear the bearing grind away. You can actually move it axially and radially.

[Don Jarvie]

Replace the motor bearing with some sealed bearings and it should be ok. The bearing may have been bad and it took all these years for it to go kaput. Replacing the motor bearings is easy enough since you have done the arbor bearings already.

[Chris Rosenberger]

Glad you found the problem. It looks like the bearings were sealed, so greasing the motor would not have helped.
Most dust gets into motors through the electrical boxes. When you put it back together, seal around the electrical boxes & power cord with clear silicone caulking.

[David Kumm]

It's not all that unusual for motor bearings to fail. they deal with some heat. Look at the code on the bearing as they should be spec'd as a motor bearing which are a little looser- I believe- to compensate. Dave

[Lee Schierer]

I'm really suprised the v-belts (power twist by fenner drives) are acting like they are.

PS... i'm new to sawmill creek and I love it. What a great community of people.

No matter what price you pay for link belts, they are not suited for use on machines with more than one belt running in tandem. The slight differences in length will make one belt work harder than the one next to it. Get a pair of matched belts and your problem should go away.

[Peter Quinn]

Glad you found the problem, I have the same saw, no motor issues to date. I'd get a matched set of VX belts, leave the link belts for the craftsman saws or keep them for a rainy day when some odd belt you can get brake and you need to keep working. I don't see those as a real solution, particularly on multi pulley machines.